treechildren::-moz-tree-checkbox(checked)
{
    /* css for checked cells */
    list-style-image: url("chrome://fontsdownloader/skin/webfontdownloader-16x16.png") !important;
}

treechildren::-moz-tree-checkbox
{
    /* css for checked cells */
    list-style-image: url("chrome://fontsdownloader/skin/webfontdownloader-16x16-unchecked.png");
}

